When handling optical fibers intended for telecommunication in connection with splicing the fibers movable retainers are used, which generally have the shape of low rectangular blocks including lids, which securely clamps the fiber or fibers. The retainer including inserted fibers is placed in a more or less accurate way in the machines or devices used, such as in a fiber welding machine on movable blocks, see for example Swedish patent application 9300578-3, which discloses a fiber welding device for fiber ribbons, such as when removing a protective sleeve and cutting optical fibers, see Swedish patent application 9103492-6, which discloses a combined stripping and cutting device for optical fibers, and when simultaneously handling a plurality of individual optical fibers placed in parallel, see Swedish patent application 9401421-4, which discloses a fiber organizer to be used when welding a plurality of optical fibers to for example the fibers of a fiber ribbon.
An optical fiber ribbon comprises a plurality of optical fibers placed at each other, isolated from each other and from the surroundings, but in some way secured in parallel at each other, e.g. by a polymer sleeve. The number of fibers, which in this way are mounted in parallel to each other, is arbitrary but fiber ribbons comprising 4 parallel fibers, so called 4 fiber ribbons, and 6, 8 fiber and 12 fiber ribbons comprising 6, 8 or 12 parallel optical fibers respectively which are retained at each other are commercially used.
In the prior art typically a loose or movable fiber retainer can be attached in a somewhat more or less definite position on a movable block, which is moved in all three coordinate directions for alignment in the welding operation. V-grooves and other devices having surfaces located in angles to each other can alternatively be used in order to accurately position the ends of the optical fibers in lateral and/or height directions and then also high requirements are posed on an accurate rigid positioning of the fiber retainer in height and lateral directions.
However, such alignment can without large problems be achieved for simple fibers owing to the fact that optical standard fibers usually have the same exterior diameter of about 250 .mu.m. In the published British patent application No. 2 303 223 for example a device is disclosed for welding optical PM fibers having stationary surfaces which are intended for a fine-positioning and are located in right angles to each other, in which device a retainer is placed accurately in height and lateral directions by bringing it, by means of magnetic forces, to engage with a fixed longitudinal projecting rib on a horizontal base surface.
However, the width of fiber ribbons present variations and differ between different brands, whereas the height from the bottom side of the fiber ribbon to the centre axis of the optical fibers included in the fiber ribbon only present insignificant variations. A loose retainer intended to be capable of being used when welding different types of fiber ribbons must therefore be capable of being displaced laterally on a fixed base surface in order that the ends of the optical fibers, which has been rid of primary and secondary protective enclosures, i.e. from the individual polymer sleeves, which surround and isolate each fiber individually, and the material or the sleeve respectively, which keeps the fibers coated with a primary coating together to form a fiber ribbon, will be capable of extending, as straight as possible, from the retainer to and through the fixedly arranged V-grooves or in any case without any bending laterally and most preferably always without any S-shaped bending in this region.
A simple small bending upwards, so that the fiber ends are still always located in a vertical plane extending from the retainer to the V-grooves, in order that the fibers by their own elasticity will remain in the V-grooves can be allowed, see the above-cited Swedish patent application 9300578-3. It must also be possible to adjust the position of the retainer by a parallel displacement, i.e. so that the retainer maintains the same angular position during the displacement and thus is not rotated, neither around a horizontal or a vertical axis.
Furthermore, it should for this case also be possible to secure such a retainer laterally in a suitable selected position, after having placed the optical fibers included in the fiber ribbon as straight as possible from the retainer to the fine alignment means having the shape of the V-grooves. The fiber ribbon must be firmly retained in the selected position laterally during the fine positioning in the longitudinal direction of the fiber ribbon, which is always necessary in order that the end surfaces of the individual opposite fibers will come in contact with each other and which is made by the displacing the blocks, on which the retainers are secured, in this direction, see the cited Swedish patent application 9300578-3.
The Japanese patent application No. 1-129 208 discloses a loose fiber retainer or jig 1, which can be placed in a fiber welding device and be clamped in it by means of clamping means 2. The German patent document No. 40 18 226 discloses a device for positioning optical fibers in connection with a welding operation. The published German patent application No. 40 06 799 is concerned with welding two groups of optical fibers to each other and discloses a retainer means and its attachment to a base. The published German patent application No. 40 25 351 also deals with welding two groups of optical fibers using a retainer.